Method for preparing a catalyst containing an active nickel phase and a nickel-copper alloy

Abstract

The invention relates to a method for preparing a catalyst containing nickel and copper and a porous alumina support, comprising the following steps of : a) bringing the alumina support into contact with a solution containing a nickel precursor and a first organic compound having at least one carboxylic acid function; b) drying at a temperature below 250°C, then calcining at a temperature of between 250°C and 550°C; c) bringing the calcined catalyst precursor obtained at the end of step b) into contact with a solution containing a nickel precursor, a copper precursor and a second organic compound having at least one carboxylic acid function; d) drying at a temperature below 250°C.

Description

technical field

[0001] The present invention relates to a supported metallic catalyst based on nickel and copper intended particularly for the hydrogenation of unsaturated hydrocarbons, and more particularly, for the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatics. State of the art

[0002] Selective hydrogenation catalysts for polyunsaturated compounds or aromatics are generally based on metals from group VIII of the periodic table, such as nickel. The metal is in the form of nanometric metallic particles deposited on a support, which may be a refractory oxide. The group VIII metal content, the possible presence of a second metallic element, the size of the metal particles, the distribution of the active phase within the support, and the nature and porosity of the support are parameters that can influence catalyst performance.

[0003] The rate of the hydrogenation reaction is governed by several criteria, such as the diffusion of reactants towards the surface of the catalyst (external diffusional limitations), the diffusion of reactants in the porosity of the support towards the active sites (internal diffusional limitations) and the intrinsic properties of the active phase such as the size of the metallic particles and the distribution of the active phase within the support.

[0004] To achieve improved catalytic performance, particularly enhanced selectivity and / or activity, it is known in the prior art to use organic compound additives for the preparation of selective hydrogenation metal catalysts. For example, application FR2984761 discloses a process for preparing a selective hydrogenation catalyst comprising a support and an active phase comprising a Group VIII metal. The catalyst is prepared by a process comprising a step of impregnating the support with a solution containing a precursor of the Group VIII metal and an organic additive, more specifically an organic compound having one to three carboxylic acid functional groups, a step of drying the impregnated support, and a step of calcining the dried support to obtain the catalyst.

[0005] Furthermore, the use of nickel-based catalysts has frequently been proposed to improve performance in selective hydrogenation. For example, US patent 5,208,405 describes the implementation of a nickel-silver-based catalyst for the selective hydrogenation of C4-C10 diolefins. Additionally, it is known to promote the use of nickel, which is the predominant component, with Group IB metals, particularly gold (FR 2,949,077) or tin (FR 2,949,078). Document FR 3,011,844 discloses a catalyst for implementing a selective hydrogenation process comprising a support and an active metallic phase deposited on the support, the active metallic phase comprising copper and at least one nickel or cobalt metal in a Cu:(Ni and / or Co) molar ratio greater than 1.

[0006] Finally, prior to using such catalysts and implementing them in a hydrogenation process, a reduction treatment step in the presence of a reducing gas is carried out to obtain a catalyst comprising an active phase at least partially in metallic form. This treatment activates the catalyst and forms metallic particles. This treatment can be carried out in-situ or ex-situ, that is, after or before loading the catalyst into the hydrogenation reactor.

[0007] Document FR3099390A1 discloses a catalyst comprising nickel and copper, with nickel content between 1 and 50% by weight relative to the total weight of the catalyst, and copper content between 0.5 and 15% by weight relative to the total weight of the catalyst, and an alumina support, said catalyst being obtained by a preparation process comprising the following steps: a) the alumina support is contacted with at least one solution containing at least one nickel precursor; b) the alumina support is contacted with at least one solution containing at least one nickel precursor and at least one copper precursor; c) the alumina support is contacted with at least one solution containing at least one organic compound comprising at least one carboxylic acid function, or at least one alcohol function, or at least one ester function, or at least one amide function, or at least one amine function, it being understood that: steps a), b) and c) are carried out separately, in any order, or steps a) and c) are carried out simultaneously, step b) being carried out either before or after the combination of steps a) and c); steps b) and c) are carried out simultaneously, step a) being carried out either before or after the combination of steps b) and c);d) at least one drying step of the catalyst precursor obtained at the end of steps a) to c) is carried out at a temperature below 250°C; e) a reduction step of the catalyst precursor obtained at the end of step d) is carried out by contacting said precursor with a reducing gas at a temperature greater than or equal to 150°C and less than 250°C.

[0008] Continuing its research in the field of catalysts for the selective hydrogenation of polyunsaturated compounds or the hydrogenation of aromatics, the Applicant has now identified that a particularly active catalyst can be prepared by carrying out a specific preparation process in which a metallic phase based on nickel and copper is added in the presence of a particular organic additive to the catalyst after the deposition of the precursor of the active phase based on nickel and also in the presence of a particular organic additive.

[0009] Without wishing to be bound by any theory, it has been observed by the Applicant that during the preparation of the catalyst, carrying out a step of contacting the catalyst with a solution simultaneously containing a copper-based metallic precursor, a nickel-based metallic precursor, and a particular organic additive, followed by a drying and reduction step in the presence of a reducing gas at low temperature (greater than or equal to 150°C and less than 200°C) makes it possible to obtain a nickel-copper alloy (in reduced form) which unexpectedly makes it possible to greatly improve the reducibility of the active nickel phase on the support, said active nickel phase being supplied in a step prior to the formation of the nickel-copper alloy (in reduced form).The preparation process according to the invention thus makes it possible to carry out a reduction step of metallic elements in the presence of a reducing gas at lower temperatures and shorter reaction times than those commonly used in the prior art. Advantageously, the use of less severe operating conditions than in the prior art allows the reduction step to be carried out directly within the reactor in which the hydrogenation of aromatic compounds is to be performed. However, the addition of nickel and copper after the addition of the active nickel phase inevitably leads to the growth of nickel particles and therefore to a substantial loss of activity. This is why the Applicant has identified that the addition of a specific organic additive, at levels much higher than those used during the impregnation of the active nickel phase, makes it possible to limit the growth of nickel particles or even to avoid it entirely. Objects of the invention

[0010] The present invention relates to a process for preparing a catalyst comprising nickel and copper, in amounts of 1 to 50% by weight of nickel relative to the total weight of the catalyst, and in amounts of 0.5 to 15% by weight of copper relative to the total weight of the catalyst, and a porous alumina support, the size of the nickel particles in the catalyst, measured in oxide form, being less than 5 nm, which process comprises at least the following steps: a) The alumina support is contacted with at least one solution containing at least one first nickel precursor and at least one first organic compound comprising at least one carboxylic acid function to obtain a first catalyst precursor; b) The first catalyst precursor obtained at the end of step a) is dried at a temperature below 250°C and then the dried first catalyst precursor is calcined at a temperature between 250°C and 550°C to obtain a calcined catalyst precursor; c) The calcined catalyst precursor obtained at the end of step b) is contacted with at least one solution containing at least one second nickel precursor, at least one copper precursor and at least one second organic compound comprising at least one carboxylic acid function to obtain a second catalyst precursor; d) The second catalyst precursor obtained at the end of step c) is dried at a temperature below 250°C.

[0011] According to one or more embodiments, the molar ratio between said organic compound introduced in step a) and the element nickel also introduced in step a) is between 0.01 and 5.0 mol / mol.

[0012] According to one or more embodiments, the molar ratio between said organic compound introduced in step c) and the element nickel also introduced in step c) is between 0.02 and 5 mol / mol.

[0013] According to one or more embodiments, the molar ratio between the nickel introduced during steps a) and c) and the copper introduced during step c) is between 0.5 and 5 mol / mol.

[0014] According to one or more embodiments, the ratio between the molar ratio between the second organic compound and the nickel introduced in step c) and the molar ratio between the first organic compound and the nickel introduced in step a) is greater than 1.5.

[0015] According to one or more embodiments, steps a) and b) are carried out at least twice before carrying out step c).

[0016] According to one or more embodiments, the first organic compound of step a) and the second organic compound of step c) are chosen from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid, pyruvic acid, levulinic acid.

[0017] According to one or more embodiments, the first organic compound of step a) and the second organic compound of step c) are identical.

[0018] According to one or more embodiments, the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide and copper fluoride.

[0019] According to one or more embodiments, the first nickel precursor and / or the second nickel precursor is nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate.

[0020] According to one or more embodiments, said process further includes a step e) in which the catalyst obtained at the end of step d) is calcined at a temperature between 250°C and 550°C.

[0021] According to one or more embodiments, said process further includes a step f) in which the catalyst obtained at the end of step d), optionally obtained at the end of step e), is reduced by bringing said catalyst into contact with a reducing gas at a temperature greater than or equal to 150°C and less than 250°C.

[0022] Another object according to the invention relates to a catalyst obtained by the preparation process according to the invention.

[0023] Another object of the invention relates to a process for the selective hydrogenation of polyunsaturated compounds containing at least two carbon atoms per molecule, contained in a hydrocarbon feedstock having a final boiling point of 300°C or less. This process is carried out at a temperature between 0 and 300°C, at a pressure between 0.1 and 10 MPa, at a molar ratio of hydrogen to polyunsaturated compounds to be hydrogenated between 0.1 and 10, and at a volumetric flow rate between 0.1 and 200 h⁻¹ when the process is carried out in the liquid phase, or at a molar ratio of hydrogen to polyunsaturated compounds to be hydrogenated between 0.5 and 1000 and at a volumetric flow rate between 100 and 40,000 h⁻¹ when the process is carried out in the gas phase, in the presence of a catalyst according to the invention or obtained according to the preparation process according to the invention.

[0024] Another object according to the invention relates to a process for hydrogenating at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point less than or equal to 650°C, said process being carried out in the gaseous or liquid phase, at a temperature between 30 and 350°C, at a pressure between 0.1 and 20 MPa, at a molar ratio of hydrogen / (aromatic compounds to be hydrogenated) between 0.1 and 10 and at an hourly volumetric rate between 0.05 and 50 h⁻¹, in the presence of a catalyst according to the invention or obtained according to the preparation process according to the invention. Detailed description of the invention 1. Definitions

[0025] In what follows, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII (or VIIIB) according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

[0026] In this description, according to the IUPAC convention, micropores are pores with a diameter less than 2 nm, i.e. 0.002 µm; mesopores are pores with a diameter greater than or equal to 2 nm, i.e. 0.002 µm and less than or equal to 50 nm, i.e. 0.05 µm; and macropores are pores with a diameter greater than 50 nm, i.e. 0.05 µm.

[0027] The total pore volume is measured by mercury porosimetry according to ASTM D4284-92 with a wetting angle of 140°, for example using a Micromeritics Autopore III™ device.

[0028] The specific surface area of ​​BET is measured by nitrogen physisorption according to the ASTM D3663-03 standard, a method described in the book Rouquerol F.; Rouquerol J.; Singh K. “Adsorption by Powders & Porous Solids: Principle, methodology and applications”, Academic Press, 1999.

[0029] The median mesoporous diameter is also defined as the diameter such that all pores, among all pores constituting the mesoporous volume, smaller than this diameter constitute 50% of the total mesoporous volume determined by mercury porosimeter intrusion.

[0030] The term "nickel particle size" refers to the diameter of nickel crystallites in their oxide form. The diameter of nickel crystallites in their oxide form is determined by X-ray diffraction, from the width of the diffraction line located at the angle 2θ = 43° (i.e., along the crystallographic direction

[200] ) using Scherrer's relation. This method, used in X-ray diffraction on powders or polycrystalline samples, relates the full width at half maximum (FWHM) of the diffraction peaks to the particle size. It is described in detail in the reference: Appl. Cryst. (1978), 11, 102-113 "Scherrer after sixty years: A survey and some new results in the determination of crystallite size", J.I. Langford and A.J.C. Wilson.

[0031] Nickel and copper content is measured by X-ray fluorescence.

[0032] In this description, the term "include" is synonymous with (means the same as) "include" and "contain," and is inclusive or open-ended, not excluding other unstated elements. It is understood that the term "include" includes the exclusive and closed term "consist." Furthermore, in this description, the term "approximately" corresponds to an approximation of ±10%, preferably ±5%, most preferably ±2%, of a reference value such as a distance, speed, flow rate, compound content, temperature, pressure, etc. 2. Process for preparing the catalyst

[0033] The steps of said preparation process are described in detail below. Step a) Contacting the support with a first nickel precursor and a first organic compound

[0034] The deposition of the first nickel precursor and the first organic compound comprising at least one carboxylic acid function on said support, in accordance with the implementation of step a), may be carried out by impregnation, dry or in excess, or by deposition-precipitation, according to methods well known to those skilled in the art.

[0035] Preferably, said step a) is carried out by dry impregnation, which consists of bringing the catalyst support into contact with a solution, containing at least the first nickel precursor and at least a first organic compound comprising a carboxylic aid function, the volume of the solution being between 0.25 and 1.5 times the porous volume of the support to be impregnated.

[0036] This step (a) is preferably carried out by impregnating the support, for example by contacting said support with at least one aqueous or organic solution (for example, methanol, ethanol, phenol, acetone, toluene, or dimethyl sulfoxide (DMSO)), or a solution consisting of a mixture of water and at least one organic solvent, containing at least the first nickel precursor at least partially dissolved and at least one first organic compound comprising a carboxylic acid group, or by contacting said support with at least one colloidal solution of at least one nickel precursor, in oxidized form (nickel oxide, oxy(hydroxide), or hydroxide nanoparticles) or in reduced form (reduced nickel metallic nanoparticles) and at least one first organic compound comprising a carboxylic acid group. Preferably, the solution is aqueous.The pH of this solution can be modified by the possible addition of an acid or a base.

[0037] Preferably, the first nickel precursor is introduced in aqueous solution, for example, as nitrate, carbonate, acetate, chloride, oxalate, complexes formed by a polyacid or an acid-alcohol and its salts, complexes formed with acetylacetonates, or any other aqueous-soluble inorganic derivative, which is then brought into contact with the support. Preferably, nickel nitrate, nickel chloride, nickel acetate, or nickel hydroxycarbonate are advantageously used as the first nickel precursor. Most preferably, the first nickel precursor is nickel nitrate.

[0038] The concentration of nickel in solution is adjusted according to the porous volume of the support still available so as to obtain for the supported catalyst, a nickel content of between 1 and 50% by weight in nickel element relative to the total weight of the catalyst, more preferably between 2 and 40% by weight and even more preferably between 3 and 35% by weight and even more preferably between 5 and 28% by weight.

[0039] The first organic compound comprising at least one carboxylic acid functional group may be an aliphatic organic compound, saturated or unsaturated, or an aromatic organic compound. Preferably, the aliphatic organic compound, saturated or unsaturated, comprises between 1 and 9 carbon atoms, preferably between 2 and 7 carbon atoms. Preferably, the aromatic organic compound comprises between 7 and 10 carbon atoms, preferably between 7 and 9 carbon atoms.

[0040] Said first aliphatic organic compound, saturated or unsaturated, or said aromatic organic compound, comprising at least one carboxylic acid function, may be chosen from monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids.

[0041] Advantageously, the first organic compound comprising at least one carboxylic acid function is chosen from ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), pentanedioic acid (glutaric acid), hydroxyacetic acid (glycolic acid), 2-hydroxypropanoic acid (lactic acid), 2-hydroxypropanedioic acid (tartronic acid), 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 2-oxopropanoic acid (pyruvic acid), 4-oxopentanoic acid (levulinic acid).

[0042] Advantageously, the molar ratio between the first organic compound introduced in step a) and the nickel element also introduced in step a) is between 0.01 and 5.0 mol / mol, preferably between 0.05 and 2.0 mol / mol, more preferably between 0.1 and 1.5 mol / mol and even more preferably between 0.3 and 1.2 mol / mol. Step b) Drying and calcination

[0043] The first catalyst precursor obtained at the end of step a) is then dried at a temperature below 250°C, preferably between 15°C and 180°C, more preferably between 30°C and 160°C, even more preferably between 50°C and 150°C, and even more preferably between 70°C and 140°C, for a period typically between 0.5 hours and 12 hours, and more preferably between 0.5 hours and 5 hours. Longer drying times are not excluded, but do not necessarily provide any improvement.

[0044] The drying stage can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere, an atmosphere containing oxygen, or a mixture of inert gases and oxygen. It is advantageously carried out at atmospheric pressure or reduced pressure. Preferably, this stage is carried out at atmospheric pressure and in the presence of air or nitrogen.

[0045] After drying, the first dried catalyst precursor is calcined at a temperature between 250°C and 600°C, preferably between 350°C and 550°C, for a period typically between 0.5 and 24 hours, preferably between 0.5 and 12 hours, and even more preferably between 0.5 and 10 hours, preferably under an inert atmosphere or an atmosphere containing oxygen. Longer durations are not excluded, but do not necessarily provide any improvement. Step c) Contacting the calcined catalyst precursor with a copper precursor, a second nickel precursor, and a second organic compound

[0046] The deposition of nickel, copper and the second organic compound comprising at least one carboxylic acid function on the calcined catalyst precursor obtained at the end of step b) can be carried out by impregnation, dry or in excess, or by deposition-precipitation, according to methods well known to those skilled in the art.

[0047] Preferably, said step c) is carried out by dry impregnation, which consists of bringing the calcined catalyst precursor into contact with a solution, comprising preferably consisting of at least one nickel precursor, at least one copper precursor, and at least one second organic compound comprising at least one carboxylic acid function, the volume of the solution being between 0.25 and 1.5 times the porous volume of the support to be impregnated.

[0048] Said step c) is preferably carried out by simultaneous impregnation of the calcined catalyst precursor obtained at the end of step b) consisting, for example, of contacting said calcined catalyst precursor with at least one aqueous or organic solution (for example, methanol or ethanol or phenol or acetone or toluene or dimethyl sulfoxide (DMSO)) or consisting of a mixture of water and at least one organic solvent, comprising, preferably consisting of, at least one second nickel precursor at least partially dissolved, at least one copper precursor at least partially dissolved and a second organic compound comprising at least one carboxylic acid function, or alternatively, of contacting said calcined catalyst precursor with at least one colloidal solution comprising, preferably consisting of,at least one nickel precursor and one copper precursor in oxidized form (nickel and copper oxide, oxy(hydroxide), or hydroxide nanoparticles) or in reduced form (reduced nickel and copper metallic nanoparticles), and at least one second organic compound comprising at least one carboxylic acid functional group. Preferably, the solution is aqueous. The pH of this solution can be modified by the optional addition of an acid or a base.

[0049] Preferably, said second nickel precursor and the copper precursor are introduced into aqueous solution.

[0050] When the second nickel precursor is introduced in aqueous solution, it is advantageously used in the form of nitrate, carbonate, acetate, chloride, hydroxide, hydroxycarbonate, oxalate, sulfate, formate, complexes formed by a polyacid or an acid-alcohol and its salts, complexes formed with acetylacetonates, tetrammine or hexammine complexes, or any other inorganic derivative soluble in aqueous solution, which is brought into contact with said catalyst precursor. Preferably, nickel nitrate, nickel hydroxide, nickel carbonate, nickel chloride, or nickel hydroxycarbonate are advantageously used as the second nickel precursor. Most preferably, the second nickel precursor is nickel nitrate, nickel carbonate, or nickel hydroxide.

[0051] When a copper precursor is introduced into aqueous solution, a copper precursor in mineral or organic form is advantageously used. In mineral form, the copper precursor can be chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide, or copper fluoride. Copper nitrate is the preferred precursor salt.

[0052] The second nickel precursor is advantageously supplied at step c) at a concentration desired to obtain on the final catalyst (i.e. obtained at the end of step d) of drying / calcination or step e) of reduction if the latter is carried out) a content of between 0.5 and 10 wt% of nickel element relative to the total weight of the final catalyst, preferably between 0.5 and 8 wt%, more preferably between 1 and 7 wt%, even more preferably between 1 and 5 wt%.

[0053] The quantities of copper precursor(s) introduced into the solution according to step c) are chosen in such a way that the total copper content is between 0.5 and 15% by weight as elemental copper relative to the total weight of the final catalyst (i.e. obtained at the end of step d) of drying / calcination or step e) of reduction if the latter is carried out), preferably between 0.5 and 12% by weight, preferably between 0.75 and 10% by weight, and even more preferably between 1 and 9% by weight.

[0054] The second organic compound comprising at least one carboxylic acid functional group may be an aliphatic organic compound, saturated or unsaturated, or an aromatic organic compound. Preferably, the aliphatic organic compound, saturated or unsaturated, comprises between 1 and 9 carbon atoms, preferably between 2 and 7 carbon atoms. Preferably, the aromatic organic compound comprises between 7 and 10 carbon atoms, preferably between 7 and 9 carbon atoms.

[0055] Said second aliphatic organic compound, saturated or unsaturated, or said aromatic organic compound, comprising at least one carboxylic acid function, may be chosen from monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids.

[0056] Advantageously, the second organic compound comprising at least one carboxylic acid function is chosen from ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), pentanedioic acid (glutaric acid), hydroxyacetic acid (glycolic acid), 2-hydroxypropanoic acid (lactic acid), 2-hydroxypropanedioic acid (tartronic acid), 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 2-oxopropanoic acid (pyruvic acid), 4-oxopentanoic acid (levulinic acid).

[0057] Advantageously, the molar ratio between the second organic compound introduced in step c) and the nickel element also introduced in step c) is between 0.02 and 5 mol / mol, preferably between 0.1 and 3 mol / mol, more preferably between 0.2 and 2 mol / mol and even more preferably between 0.3 and 2 mol / mol.

[0058] Advantageously, the ratio between the molar ratio of the second organic compound to the nickel introduced in step c) and the molar ratio of the first organic compound to the nickel introduced in step a) is greater than or equal to 1.5, preferably between 2 and 5.

[0059] Advantageously, the second organic compound introduced in step c) is identical to the first organic compound introduced in step a). Step d) Drying

[0060] The second catalyst precursor obtained at the end of step c) is then dried at a temperature below 250°C, preferably between 15°C and 180°C, more preferably between 30°C and 160°C, even more preferably between 50°C and 150°C, and even more preferably between 70°C and 140°C, for a period typically between 0.5 hours and 12 hours, and more preferably between 0.5 hours and 5 hours. Longer drying times are not excluded, but do not necessarily provide any improvement.

[0061] The drying stage can be carried out by any technique known to those skilled in the art. It is advantageously carried out under an inert atmosphere, an atmosphere containing oxygen, or a mixture of inert gases and oxygen. It is advantageously carried out at atmospheric pressure or reduced pressure. Preferably, this stage is carried out at atmospheric pressure and in the presence of air or nitrogen. Step e) calcination (optional)

[0062] After drying, the catalyst obtained at the end of step d) is advantageously calcined at a temperature between 250°C and 600°C, preferably between 350°C and 550°C, for a period typically between 0.5 and 24 hours, preferably between 0.5 and 12 hours, and even more preferably between 0.5 and 10 hours, preferably under an inert atmosphere or an atmosphere containing oxygen. Longer durations are not excluded, but do not necessarily provide any improvement. Step f) Reduction by a reducing gas (optional)

[0063] In one embodiment according to the invention, prior to using the catalyst in the catalytic reactor and implementing a hydrogenation process, a reduction treatment step f) is carried out in the presence of a reducing gas so as to obtain a catalyst comprising nickel at least partially in metallic form. This step is advantageously carried out in-situ That is, after the catalyst is loaded into a hydrogenation reactor. This treatment activates the catalyst and forms metallic particles, particularly zero-valent nickel. The process in-situThe reduction treatment of the catalyst eliminates the need for an additional passivation step using an oxygenated compound or CO2, which is necessary when the catalyst is prepared by ex-situ reduction treatment, i.e., outside the reactor used for the hydrogenation of aromatic or polyaromatic compounds. Indeed, when the reduction treatment is carried out ex-situ, a passivation step is required to protect the metallic phase of the catalyst in the presence of air (during transport and loading of the catalyst into the hydrogenation reactor), followed by a further reduction step.

[0064] The reducing gas is preferably hydrogen. Hydrogen can be used pure or in a mixture (for example, a hydrogen / nitrogen, hydrogen / argon, or hydrogen / methane mixture). When hydrogen is used in a mixture, any proportion is possible.

[0065] The said reduction treatment is carried out at a temperature greater than or equal to 150°C and less than 250°C, preferably between 160 and 230°C, and more preferably between 170 and 220°C. The duration of the reduction treatment is between 5 minutes and less than 5 hours, preferably between 10 minutes and 4 hours, and even more preferably between 10 minutes and 210 minutes.

[0066] The presence of the nickel-copper alloy at least partially in reduced form allows for the use of less severe operating conditions for the reduction of the active nickel phase than in the prior art and thus allows the reduction step to be carried out directly within the reactor in which the hydrogenation of unsaturated or aromatic compounds is to be carried out.

[0067] Furthermore, the presence of copper in the catalyst helps maintain good catalyst activity and a long service life when it comes into contact with a hydrocarbon feed containing sulfur. Indeed, compared to nickel, the copper in the catalyst more readily captures sulfur compounds from the feed, thus limiting irreversible poisoning of the active sites. The temperature rise to the desired reduction temperature is generally slow, for example, set between 0.1 and 10°C / min, preferably between 0.3 and 7°C / min.

[0068] The hydrogen flow rate, expressed in L / hour / gram of catalyst precursor, is between 0.01 and 100 L / hour / gram of catalyst, preferably between 0.05 and 10 L / hour / gram of catalyst precursor, even more preferably between 0.1 and 5 L / hour / gram of catalyst precursor. 3. Catalyst

[0069] The preparation process according to the invention makes it possible to obtain a catalyst comprising nickel and copper, with 1 to 50% by weight of nickel element relative to the total weight of the catalyst, and with 0.5 to 15% by weight of copper element relative to the total weight of the catalyst, and a porous alumina support, the size of the nickel particles in the catalyst, measured in oxide form, being less than 5 nm.

[0070] Preferably, at least part of the nickel and copper is in the form of a nickel-copper alloy, advantageously conforming to the formula Ni x Cu y with x between 0.1 and 0.9 and y between 0.1 and 0.9.

[0071] Preferably, the nickel content included in the copper-nickel alloy is between 0.5 and 15% by weight as nickel element relative to the total weight of the catalyst, preferably between 1 and 12% by weight, and more preferably between 1 and 10% by weight.

[0072] The size of nickel particles, measured in oxide form, in the catalyst is less than 5 nm, more preferably less than 4 nm, and even more preferably less than or equal to 3 nm.

[0073] The nickel content in said catalyst is advantageously between 1 and 50% by weight relative to the total weight of the catalyst, more preferably between 2 and 40% by weight, and even more preferably between 3 and 35% by weight, and even more preferably between 5 and 25% by weight relative to the total weight of the catalyst.

[0074] The copper content is between 0.5 and 15% by weight as elemental copper relative to the total weight of the catalyst, preferably between 0.5 and 12% by weight, preferably between 0.75 and 10% by weight, and even more preferably between 1 and 9% by weight.

[0075] The specific surface area of ​​the catalyst is generally between 10 m² / g and 350 m² / g, preferably between 25 m² / g and 300 m² / g, more preferably between 40 m² / g and 250 m² / g.

[0076] The total porous volume of the catalyst is generally between 0.1 and 1 ml / g, preferably between 0.2 ml / g and 0.8 ml / g, and particularly preferably between 0.3 ml / g and 0.7 ml / g.

[0077] The active phase of the catalyst preferably does not include any metal from group VIB. In particular, it does not include molybdenum or tungsten.

[0078] The catalyst (and the support used for its preparation) is in the form of grains advantageously having a diameter of between 0.5 and 10 mm. The grains may have any shape known to those skilled in the art, for example, spheres (preferably with a diameter of between 1 and 8 mm), extrudates, tablets, or hollow cylinders. Preferably, the catalyst (and the support used for its preparation) is in the form of extrudates with a diameter of between 0.5 and 10 mm, preferably between 0.8 and 3.2 mm, and most preferably between 1.0 and 2.5 mm, and a length of between 0.5 and 20 mm. The "diameter" of the extrudates is understood to mean the diameter of the circle circumscribed about the cross-section of these extrudates. The catalyst may advantageously be in the form of cylindrical, multilobed, trilobed, or quadrilobed extrudates. Preferably, its shape will be trilobed or quadrilobed.The shape of the lobes can be adjusted according to all methods known from the prior art. 4. Support

[0079] The characteristics of alumina, mentioned in this section, correspond to the characteristics of alumina before the implementation of step a) of the preparation process according to the invention.

[0080] The substrate is alumina, meaning that it comprises at least 95%, preferably at least 98%, and most preferably at least 99% by weight of alumina relative to the weight of the substrate. The alumina generally has a delta, gamma, or theta alumina crystallographic structure, either alone or in mixtures.

[0081] The alumina support may include impurities such as metal oxides of groups IIA, IIIB, IVB, IIB, IIIA, IVA according to the CAS classification, preferably silica, titanium dioxide, zirconium dioxide, zinc oxide, magnesium oxide and calcium oxide, or alkali metals, preferably lithium, sodium or potassium, and / or alkaline earth metals, preferably magnesium, calcium, strontium or barium, or sulfur.

[0082] The specific surface area of ​​alumina is generally between 10 m² / g and 400 m² / g, preferably between 30 m² / g and 350 m² / g, more preferably between 50 m² / g and 300 m² / g.

[0083] The pore volume of alumina is generally between 0.1 ml / g and 1.2 ml / g, preferably between 0.3 ml / g and 0.9 ml / g, and most preferably between 0.5 ml / g and 0.9 ml / g.

[0084] The mesoporous median diameter is advantageously between 3 nm and 25 nm, and preferably between 6 and 20 nm, and particularly preferably between 8 and 18 nm. 5. Selective hydrogenation process

[0085] The present invention also relates to a process for the selective hydrogenation of polyunsaturated compounds containing at least two carbon atoms per molecule, such as diolefins and / or acetylenic and / or alkenylaromatic compounds, also called styrenics, contained in a hydrocarbon feedstock having a final boiling point of 300°C or less, which process is carried out at a temperature between 0 and 300°C, at a pressure between 0.1 and 10 MPa, at a molar ratio of hydrogen to (polyunsaturated compounds to be hydrogenated) between 0.1 and 10, and at a volumetric flow rate between 0.1 and 200 h⁻¹ when the process is carried out in the liquid phase, or at a molar ratio of hydrogen to (polyunsaturated compounds to be hydrogenated) between 0.5 and 1000 and at a volumetric flow rate between 100 and 40000 h -1 < when the process is carried out in the gaseous phase,in the presence of a catalyst obtained by the preparation process as described above.

[0086] Monounsaturated organic compounds, such as ethylene and propylene, are the basis for the manufacture of polymers, plastics, and other value-added chemicals. These compounds are obtained from natural gas, naphtha, or diesel fuel that has been processed by steam cracking or catalytic cracking. These processes are carried out at high temperatures and produce, in addition to the desired monounsaturated compounds, polyunsaturated organic compounds such as acetylene, propadiene and methylacetylene (or propyne), 1,2-butadiene and 1,3-butadiene, vinylacetylene and ethylacetylene, and other polyunsaturated compounds with a boiling point corresponding to the C5+ fraction (hydrocarbon compounds with at least 5 carbon atoms), particularly diolefinic, styrenic, or indenic compounds. These polyunsaturated compounds are highly reactive and lead to unwanted reactions in polymerization units.It is therefore necessary to eliminate them before utilizing these cuts.

[0087] Selective hydrogenation is the primary treatment developed to specifically remove undesirable polyunsaturated compounds from these hydrocarbon feedstocks. It allows the conversion of polyunsaturated compounds to the corresponding alkenes or aromatics while preventing their complete saturation and thus the formation of the corresponding alkanes or naphthenes. In the case of steam cracking gasoline used as feedstock, selective hydrogenation also allows the selective hydrogenation of alkenyl-aromatics into aromatics while avoiding the hydrogenation of the aromatic rings.

[0088] The hydrocarbon feedstock treated in the selective hydrogenation process has a final boiling point of 300°C or less and contains at least two carbon atoms per molecule and includes at least one polyunsaturated compound. "Polyunsaturated compounds" are defined as compounds containing at least one acetylenic group and / or at least one diene group and / or at least one alkenylaromatic group.

[0089] More specifically, the charge is selected from the group consisting of a C2 steam cracking cut, a C2-C3 steam cracking cut, a C3 steam cracking cut, a C4 steam cracking cut, a C5 steam cracking cut and a steam cracking essence also called pyrolysis essence or C5+ cut.

[0090] The C2 steam cracker cut, advantageously used for implementing the selective hydrogenation process according to the invention, has, for example, the following composition: between 40 and 95 wt% ethylene, approximately 0.1 to 5 wt% acetylene, the remainder being essentially ethane and methane. In some C2 steam cracker cuts, between 0.1 and 1 wt% of C3 compounds may also be present.

[0091] The C3 steam cracking fraction, advantageously used for implementing the selective hydrogenation process according to the invention, has, for example, the following average composition: approximately 90% by weight of propylene, approximately 1 to 8% by weight of propadiene and methylacetylene, the remainder being essentially propane. In some C3 fractions, between 0.1 and 2% by weight of C2 and C4 compounds may also be present.

[0092] A C2-C3 fraction can also be advantageously used for implementing the selective hydrogenation process according to the invention. For example, it may have the following composition: approximately 0.1 to 5 wt% acetylene, approximately 0.1 to 3 wt% propadiene and methylacetylene, approximately 30 wt% ethylene, approximately 5 wt% propylene, the remainder being essentially methane, ethane, and propane. This feedstock may also contain between 0.1 and 2 wt% C4 compounds.

[0093] The C4 steam cracking fraction, advantageously used for implementing the selective hydrogenation process according to the invention, has, for example, the following average mass composition: 1 wt% butane, 46.5 wt% butene, 51 wt% butadiene, 1.3 wt% vinylacetylene, and 0.2 wt% butyne. In some C4 fractions, between 0.1 and 2 wt% of C3 and C5 compounds may also be present.

[0094] The C5 steam cracking cut, advantageously used for implementing the selective hydrogenation process according to the invention, has for example the following composition: 21% weight of pentanes, 45% weight of pentenes, 34% weight of pentadienes.

[0095] The steam cracking gasoline, or pyrolysis gasoline, advantageously used for implementing the selective hydrogenation process according to the invention, corresponds to a hydrocarbon fraction whose boiling point is generally between 0 and 300°C, preferably between 10 and 250°C. The polyunsaturated hydrocarbons to be hydrogenated present in said steam cracking gasoline are, in particular, diolefinic compounds (butadiene, isoprene, cyclopentadiene, etc.), styrenic compounds (styrene, alpha-methylstyrene, etc.), and indenic compounds (indene, etc.). The steam cracking gasoline generally comprises the C5-C12 fraction with traces of C3, C4, C13, C14, and C15 (for example, between 0.1 and 3 wt% for each of these fractions).For example, a charge formed from pyrolysis gasoline generally has the following composition: 5 to 30% by weight of saturated compounds (paraffins and naphthenes), 40 to 80% by weight of aromatic compounds, 5 to 20% by weight of mono-olefins, 5 to 40% by weight of diolefins, 1 to 20% by weight of alkenyl-aromatic compounds, all compounds together making up 100%. It also contains 0 to 1000 ppm by weight of sulfur, preferably 0 to 500 ppm by weight of sulfur.

[0096] Preferably, the polyunsaturated hydrocarbon feed treated according to the selective hydrogenation process according to the invention is a C2 steam cracking cut, or a C2-C3 steam cracking cut, or a steam cracking gasoline.

[0097] The selective hydrogenation process according to the invention aims to eliminate polyunsaturated hydrocarbons present in the feedstock without hydrogenating monounsaturated hydrocarbons. For example, when the feedstock is a C2 fraction, the selective hydrogenation process aims to selectively hydrogenate acetylene. When the feedstock is a C3 fraction, the selective hydrogenation process aims to selectively hydrogenate propadiene and methylacetylene. In the case of a C4 fraction, the aim is to eliminate butadiene, vinylacetylene (VAC), and butyne; in the case of a C5 fraction, the aim is to eliminate pentadienes.When said feedstock is steam cracking gasoline, the selective hydrogenation process aims to selectively hydrogenate said polyunsaturated hydrocarbons present in said feedstock to be treated so that diolefinic compounds are partially hydrogenated into mono-olefins and that styrenic and indenic compounds are partially hydrogenated into corresponding aromatic compounds while avoiding the hydrogenation of aromatic rings.

[0098] The technological implementation of the selective hydrogenation process is, for example, carried out by injecting, in an upward or downward flow, the polyunsaturated hydrocarbon feedstock and hydrogen into at least one fixed-bed reactor. This reactor may be isothermal or adiabatic. An adiabatic reactor is preferred. The polyunsaturated hydrocarbon feedstock may advantageously be diluted by one or more reinjections of the effluent from the reactor where the selective hydrogenation reaction takes place, at various points within the reactor, located between the inlet and outlet, in order to limit the temperature gradient within the reactor. The technological implementation of the selective hydrogenation process according to the invention may also advantageously be carried out by installing at least one of the supported catalysts in a reactive distillation column, in heat exchanger reactors, or in a slurry reactor.The hydrogen flow can be introduced at the same time as the feed to be hydrogenated and / or at one or more different points in the reactor.

[0099] Selective hydrogenation of C2, C2-C3, C3, C4, C5, and C5+ steam cracking fractions can be carried out in the gas or liquid phase, preferably in the liquid phase for C3, C4, C5, and C5+ fractions and in the gas phase for C2 and C2-C3 fractions. A liquid-phase reaction reduces energy costs and increases catalyst cycle time.

[0100] In general, the selective hydrogenation of a hydrocarbon feed containing polyunsaturated compounds with at least 2 carbon atoms per molecule and a final boiling point of less than or equal to 300°C is carried out at a temperature between 0 and 300°C, at a pressure between 0.1 and 10 MPa, at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) between 0.1 and 10 and at a volumetric hourly rate (defined as the ratio of the volumetric flow rate of feed to the volume of the catalyst) between 0.1 and 200 h -1< for a process carried out in the liquid phase, or at a molar ratio of hydrogen / (polyunsaturated compounds to be hydrogenated) between 0.5 and 1000 and at a volumetric hourly rate between 100 and 40000 h -1< for a process carried out in the gaseous phase.

[0101] In an embodiment according to the invention, when a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally between 0.5 and 10, preferably between 0.7 and 5.0 and even more preferably between 1.0 and 2.0, the temperature is between 0 and 200°C, preferably between 20 and 200°C and even more preferably between 30 and 180°C, the hourly volumetric velocity (VVH) is generally between 0.5 and 100 h⁻¹, preferably between 1 and 50 h⁻¹ and the pressure is generally between 0.3 and 8.0 MPa, preferably between 1.0 and 7.0 MPa and even more preferably between 1.5 and 4.0 MPa.

[0102] More preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio hydrogen / (polyunsaturated compounds to be hydrogenated) is between 0.7 and 5.0, the temperature is between 20 and 200 °C, the hourly volumetric velocity (VVH) is generally between 1 and 50 h -1< and the pressure is between 1.0 and 7.0 MPa.

[0103] Even more preferably, a selective hydrogenation process is carried out in which the feedstock is a steam cracking gasoline comprising polyunsaturated compounds, the molar ratio hydrogen / (polyunsaturated compounds to be hydrogenated) is between 1.0 and 2.0, the temperature is between 30 and 180°C, the hourly volumetric velocity (VVH) is generally between 1 and 50 h -1< and the pressure is between 1.5 and 4.0 MPa.

[0104] The hydrogen flow rate is adjusted to ensure sufficient quantity is available to theoretically hydrogenate all polyunsaturated compounds and to maintain an excess of hydrogen at the reactor outlet.

[0105] In another embodiment of the invention, when a selective hydrogenation process is carried out in which the feedstock is a C2 steam cracker cut and / or a C2-C3 steam cracker cut comprising polyunsaturated compounds, the molar ratio (hydrogen) / (polyunsaturated compounds to be hydrogenated) is generally between 0.5 and 1000, preferably between 0.7 and 800, the temperature is between 0 and 300°C, preferably between 15 and 280°C, the hourly volumetric velocity (VVH) is generally between 100 and 40000 h-1, preferably between 500 and 30000 h-1, and the pressure is generally between 0.1 and 6.0 MPa, preferably between 0.2 and 5.0 MPa. 6. Hydrogenation process for aromatics

[0106] The present invention also relates to a process for hydrogenating at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point less than or equal to 650°C, generally between 20 and 650°C, and preferably between 20 and 450°C. Said hydrocarbon feedstock containing at least one aromatic or polyaromatic compound may be selected from the following petroleum or petrochemical fractions: catalytic reforming reformate, kerosene, light diesel, heavy diesel, cracking distillates, such as FCC recycled oil, coking unit diesel, hydrocracking distillates.

[0107] The aromatic or polyaromatic content of the hydrocarbon feedstock treated in the hydrogenation process according to the invention is generally between 0.1 and 80% by weight, preferably between 1 and 50% by weight, and particularly preferably between 2 and 35% by weight, the percentage being based on the total weight of the hydrocarbon feedstock. Aromatic compounds present in said hydrocarbon feedstock include, for example, benzene or alkylaromatics such as toluene, ethylbenzene, o-xylene, m-xylene, or p-xylene, or aromatics having several aromatic rings (polyaromatics) such as naphthalene.

[0108] The sulfur or chlorine content of the feed is generally less than 5000 ppm by weight of sulfur or chlorine, preferably less than 100 ppm by weight, and particularly preferably less than 10 ppm by weight.

[0109] The technological implementation of the aromatic or polyaromatic compound hydrogenation process is, for example, carried out by injecting the hydrocarbon feedstock and hydrogen into at least one fixed-bed reactor, either in an upward or downward flow. This reactor may be isothermal or adiabatic. An adiabatic reactor is preferred. The hydrocarbon feedstock may advantageously be diluted by one or more reinjections of the effluent from the reactor where the aromatic hydrogenation reaction takes place, at various points within the reactor, located between the inlet and outlet, in order to limit the temperature gradient within the reactor. The technological implementation of the aromatic hydrogenation process according to the invention may also advantageously be carried out by installing at least one of the supported catalysts in a reactive distillation column, in heat exchanger reactors, or in a slurry reactor.The hydrogen flow can be introduced at the same time as the feed to be hydrogenated and / or at one or more different points in the reactor.

[0110] The hydrogenation of aromatic or polyaromatic compounds can be carried out in the gaseous phase or in the liquid phase, preferably in the liquid phase. In general, the hydrogenation of aromatic or polyaromatic compounds is carried out at a temperature between 30 and 350°C, preferably between 50 and 325°C, at a pressure between 0.1 and 20 MPa, preferably between 0.5 and 10 MPa, at a molar ratio of hydrogen / (aromatic compounds to be hydrogenated) between 0.1 and 10 and at an hourly volumetric rate between 0.05 and 50 h -1, preferably between 0.1 and 10 h -1 of a hydrocarbon feed containing aromatic or polyaromatic compounds and having a final boiling point less than or equal to 650°C, generally between 20 and 650°C, and preferably between 20 and 450°C.

[0111] The hydrogen flow rate is adjusted to ensure sufficient quantity is available to theoretically hydrogenate all aromatic compounds and to maintain an excess of hydrogen at the reactor outlet.

[0112] The conversion of aromatic or polyaromatic compounds is generally greater than 20% by mole, preferably greater than 40% by mole, more preferably greater than 80% by mole, and particularly preferably greater than 90% by mole of the aromatic or polyaromatic compounds contained in the hydrocarbon feedstock. The conversion is calculated by dividing the difference between the total moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock and in the product by the total moles of aromatic or polyaromatic compounds in the hydrocarbon feedstock.

[0113] According to a particular embodiment of the process according to the invention, a process for hydrogenating benzene from a hydrocarbon feedstock, such as reformate from a catalytic reforming unit, is carried out. The benzene content in said hydrocarbon feedstock is generally between 0.1 and 40 wt%, preferably between 0.5 and 35 wt%, and particularly preferably between 2 and 30 wt%, the wt% being based on the total weight of the hydrocarbon feedstock.

[0114] The sulfur or chlorine content of the feed is generally less than 10 ppm by weight of sulfur or chlorine respectively, and preferably less than 2 ppm by weight.

[0115] The hydrogenation of benzene contained in the hydrocarbon feedstock can be carried out in the gaseous or liquid phase, preferably in the liquid phase. When carried out in the liquid phase, a solvent may be present, such as cyclohexane, heptane, or octane. Generally, the hydrogenation of benzene is carried out at a temperature between 30 and 250°C, preferably between 50 and 200°C, and more preferably between 80 and 180°C, at a pressure between 0.1 and 10 MPa, preferably between 0.5 and 4 MPa, at a hydrogen / (benzene) molar ratio between 0.1 and 10, and at an hourly volumetric rate between 0.05 and 50 h⁻¹, preferably between 0.5 and 10 h⁻¹.

[0116] The conversion of benzene is generally greater than 50% by mole, preferably greater than 80% by mole, more preferably greater than 90% by mole and particularly preferred greater than 98% by mole.

[0117] The invention will now be illustrated by means of the following examples, which are by no means exhaustive. Examples

[0118] For all catalysts mentioned in the examples below, the support is an alumina A with a specific surface area of ​​180 m² / g, a pore volume of 0.7 mL / g and a mesoporous median diameter of 10 nm. Example 1: Preparation of an aqueous solution S1 of the first Ni precursor with a first organic compound

[0119] Aqueous solution S1 is prepared by dissolving 58 g of nickel nitrate (NiNO3, supplier Strem Chemicals®) and 14.35 g of malonic acid (CAS 141-82-2; supplier Fluka®) in 42 mL of distilled water. The solution is heated to 60°C to facilitate the dissolution of the nickel nitrate. The molar ratio of additive to Ni is set at 0.4 mol / mol. This yields solution S1. Example 2: Preparation of an aqueous solution S2 of NiCu alloy precursors (5 wt% Ni) but without a second organic compound

[0120] The aqueous solution of NiCu alloy precursors (solution S2) used for preparing NiCu-containing catalysts is prepared by dissolving 14.5 g of nickel nitrate (NiNO3, supplied by Strem Chemicals®) in 13 mL of distilled water. This yields a solution with a Ni concentration of 116.6 g per liter. The copper nitrate precursor is then added to achieve a Ni / Cu molar ratio of 1.

[0121] We obtain solution S2. It allows the introduction of the precursors of the NiCu alloy with a mass content of Ni relative to the final catalyst of 5% weight relative to the total weight of the catalyst. Example 3: Preparation of an aqueous solution S3 of the precursors of the NiCu alloy and a second organic compound (5% by weight of Ni)

[0122] The aqueous solution of NiCu alloy precursors (solution S3) used for preparing NiCu-containing catalysts is prepared by dissolving 14.5 g of nickel nitrate (NiNO3, supplied by Strem Chemicals®) in 13 mL of distilled water. This yields a solution with a Ni concentration of 116.6 g per liter. The copper nitrate precursor is then added to achieve a Ni / Cu molar ratio of 1. Malonic acid is also added to the solution to achieve an additive / Ni molar ratio of 0.90 mol / mol.

[0123] We obtain solution S3. It allows the introduction of the precursors of the NiCu alloy with a mass content of Ni relative to the final catalyst of 5% weight relative to the total weight of the catalyst. Example 4: Preparation of catalyst A (non-compliant - no second organic compound)

[0124] 10 g of alumina A are dry-impregnated with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. Next, 10 mL of solution S2, prepared in Example 2, is dry-impregnated by adding it dropwise. The resulting solid is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours.

[0125] Catalyst A is obtained containing 24% by weight of nickel relative to the total weight of the catalyst (of which 5% by weight is nickel contained within the NiCu alloy). The characteristics of catalyst A thus obtained are shown in Table 1 below. Example 5: Preparation of catalyst B (non-compliant - no second organic compound)

[0126] 10 g of alumina A are dry-impregnated with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. This intermediate catalyst is then dry-impregnated again with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. Finally, 10 mL of solution S2, prepared in Example 2, is dry-impregnated by adding it dropwise. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L / h / g of catalyst at 450°C for 2 hours.

[0127] Catalyst B is obtained, containing 27% by weight of nickel relative to the total weight of the catalyst (of which 5% by weight is nickel contained within the NiCu alloy). The characteristics of catalyst B thus obtained are shown in Table 1 below. Example 6: Preparation of a C (compliant) catalyst

[0128] 10 g of alumina A are dry-impregnated with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. Next, 10 mL of solution S3, prepared in Example 3, is dry-impregnated by adding it dropwise. The molar ratio between the second organic compound / Ni (NiCu solution, solution S2) and the first organic compound / Ni molar ratio (active Ni, solution S1) is 2.25. The resulting solid is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours.

[0129] The catalyst C obtained contains 24% by weight of the element nickel relative to the total weight of the catalyst (of which 5% by weight is the element nickel contained in the NiCu alloy). The characteristics of the catalyst C thus obtained are shown in Table 1 below. Example 7: Preparation of a D catalyst (compliant - double impregnation)

[0130] 10 g of alumina A are dry-impregnated with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. This intermediate catalyst is then dry-impregnated again with 7.1 mL of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. Finally, 10 mL of solution S3, prepared in Example 3, is dry-impregnated by adding it dropwise. The molar ratio between the 2nd organic compound / Ni (NiCu solution, solution S2) and the molar ratio 1st organic compound / Ni (active Ni solution S1) is 2.25. The solid thus obtained is then dried in an oven for 12 hours at 120°C, then calcined under a flow of dry air of 1 L / h / g of catalyst at 450°C for 2 hours.

[0131] The catalyst D obtained contains 27% by weight of the element nickel relative to the total weight of the catalyst (of which 5% by weight is nickel contained within the NiCu alloy). The characteristics of the catalyst D thus obtained are shown in Table 1 below. Example 8: Preparation of catalyst E (non-compliant - no NiCu and no second organic compound)

[0132] 10 g of alumina A are dry-impregnated with 7.1 ml of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours. This intermediate catalyst is then dry-impregnated again with 7.1 ml of solution S1. The resulting catalyst precursor is then oven-dried for 12 hours at 120°C and calcined under a dry air flow of 1 L / h / g of catalyst at 450°C for 2 hours.

[0133] The catalyst E obtained contains 22% by weight of nickel relative to the total weight of the catalyst. The characteristics of the catalyst E thus obtained are shown in Table 1 below. Table 1 Catalyst Second organic compound No. (wt%)* Particle size (nm) A (non-compliant) No 19 6 B (non-compliant) No 22 9 C (compliant) Yes 19 2,5 D (compliant) Yes 22 3 E (non-compliant) no (no NiCu) 22 5 *Ni° excluding NiCu alloy Example 9: Characterization

[0134] The quantity of alloy obtained after the calcination and reduction step was determined by X-ray diffraction (XRD) analysis on catalyst samples in powder form.

[0135] The amount of nickel in metallic form obtained after the reduction step was determined by X-ray diffraction (XRD) analysis of catalyst samples in powder form. Between the reduction step and throughout the entire XRD characterization process, the catalysts were never exposed to air. Diffraction patterns were obtained by X-ray crystallography using a diffractometer and the classical powder method with copper Kα1 radiation (λ = 1.5406 Å).

[0136] The reduction rate was calculated by calculating the area of ​​the Ni 0< line located around 52°2θ, on all the diffractograms of each analyzed catalyst sample, then subtracting the signal present from room temperature below the 52° line which is due to alumina.

[0137] Table 2 below summarizes the reduction rates, or the metallic nickel content (Ni°) (expressed as a percentage by weight relative to the total weight of "active" Ni that does not constitute the alloy), for all catalysts A to E characterized by XRD after a reduction step at 170°C for 190 minutes under a hydrogen flow. These values ​​were also compared with the reduction rate obtained for catalyst E (Ni alone) after a conventional reduction step (i.e., at a temperature of 400°C for 15 hours under a hydrogen flow).

[0138] At room temperature on all catalysts, after calcination, containing copper and nickel, we detect alumina in delta and theta form, and large NiO and CuO lines.

[0139] Furthermore, after reduction, we detect a line corresponding to the alloy in the form of Ni 0.76 Cu 0.24.

[0140] To assess the reducibility rate and thus the formation of NiO<, the area of ​​the NiO< line located around 52°2θ is measured across all diffractograms, by subtracting the signal present at room temperature below the 52° line, which is due to alumina. This allows us to determine the relative percentage of NiO< crystallized after reduction. Table 2 Catalyst Final reduction Ni / Cu Particle size (nm) Percentage of Ni° alone (DRX) after reduction (%) A (non-compliant) 170°C, 190 min Yes 6 90 B (non-compliant) 170°C, 190 min Yes 9 92 C (compliant) 170°C, 190 min Yes 2,5 90 D (compliant) 170°C, 190 min Yes 3 90 E (non-compliant) 170°C, 190 min No 4 0* E (non-compliant) 400°C, 15 h No 4 80 *Nickel in the form of NiO

[0141] For catalyst E (22% Ni alone / alumina), the nickel reducibility rate is 0% after exactly the same hydrogen reduction treatment as for catalysts A, B, C, D. Catalyst E must be reduced at 400°C to obtain a reduction of nickel oxide to Ni° of around 80%. Example 10: Catalytic tests: performance in selective hydrogenation of a mixture containing styrene and isoprene (A HYD1)

[0142] The catalysts A to E described in the examples above are tested against the selective hydrogenation reaction of a mixture containing styrene and isoprene.

[0143] The composition of the feedstock to be selectively hydrogenated is as follows: 8 wt% styrene (supplier Sigma Aldrich®, 99% purity), 8 wt% isoprene (supplier Sigma Aldrich®, 99% purity), and 84 wt% n-heptane (solvent) (supplier VWR®, >99% purity, chromanorm HPLC). This composition corresponds to the initial composition of the reaction mixture. This mixture of model molecules is representative of a pyrolysis essence.

[0144] The selective hydrogenation reaction is carried out in a 500 mL stainless steel autoclave, equipped with magnetically driven mechanical stirring and capable of operating under a maximum pressure of 100 bar (10 MPa) and temperatures between 5°C and 200°C.

[0145] In an autoclave, 214 mL of n-heptane (supplier VWR®, purity > 99% chromanorm HPLC) and 3 mL of catalyst are added. The autoclave is closed and purged. It is then pressurized to 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ,at 170 °C for 90 minutes under a hydrogen flow of 1 L / h / g (temperature ramp of 1 °C / min) for catalysts A to E (which corresponds here to step f) of the preparation process according to the invention in one embodiment). The autoclave is then brought to the test temperature of 30 °C. At time t=0, approximately 30 g of a mixture containing styrene, isoprene, n-heptane, pentanethiol, and thiophene are introduced into the autoclave. The reaction mixture then has the composition described above, and agitation is started at 1600 rpm. The pressure is maintained constant at 35 bar (3.5 MPa) in the autoclave using a reservoir bottle located upstream of the reactor.

[0146] Another test was carried out for catalyst E, but with a catalyst reduction temperature of 400°C for 15 hours.

[0147] The progress of the reaction is monitored by taking samples of the reaction mixture at regular time intervals: styrene is hydrogenated to ethylbenzene, without hydrogenation of the aromatic ring, and isoprene is hydrogenated to methyl butene. If the reaction is prolonged longer than necessary, the methyl butene is in turn hydrogenated to isopentane. Hydrogen consumption is also monitored over time by the decrease in pressure in a reservoir bottle located upstream of the reactor. The catalytic activity is expressed in moles of H₂ consumed per minute per gram of Ni.

[0148] The catalytic activities measured for catalysts A to E are reported in Table 3 below. They are related to the catalytic activity (A HYD1) measured for catalyst E prepared under classical reduction conditions (at a temperature of 400°C for 15 hours under a hydrogen flow). Example 11: Catalytic tests: performance in the hydrogenation of toluene (A HYD2)

[0149] Catalysts A to E described in the examples above are also tested with respect to the hydrogenation reaction of toluene. The selective hydrogenation reaction is carried out in the same autoclave as that described in Example 10.

[0150] In an autoclave, 214 mL of n-heptane (supplier VWR®, purity > 99% chromanorm HPLC) and 3 mL of catalyst are added. The autoclave is closed and purged. It is then pressurized to 35 bar (3.5 MPa) of hydrogen. The catalyst is first reduced in situ,at 170 °C for 90 minutes under a hydrogen flow of 1 L / h / g (temperature ramp of 1 °C / min) for catalysts A to E (which corresponds here to step f) of the preparation process according to the invention in one embodiment). After the addition of 216 mL of n-heptane (supplier VWR®, purity > 99% chromanorm HPLC), the autoclave is closed, purged, then pressurized under 35 bar (3.5 MPa) of hydrogen, and brought to the test temperature of 80 °C. At time t=0, approximately 26 g of toluene (SDS® supplier, purity > 99.8%) are introduced into the autoclave (the initial composition of the reaction mixture is then toluene 6 wt% / n-heptane 94 wt%) and agitation is started at 1600 rpm. The pressure is maintained constant at 35 bar (3.5 MPa) in the autoclave using a reservoir bottle located upstream of the reactor.

[0151] The progress of the reaction is monitored by taking samples of the reaction medium at regular time intervals: the toluene is completely hydrogenated to methylcyclohexane. Hydrogen consumption is also monitored over time by the decrease in pressure in a reservoir bottle located upstream of the reactor. The catalytic activity is expressed in moles of H₂ consumed per minute per gram of Ni.

[0152] The catalytic activities measured for catalysts A to E are reported in Table 3 below. They are related to the catalytic activity (A HYD2) measured for catalyst E prepared under conventional reduction conditions (at a temperature of 400°C for 15 hours under a hydrogen flow). Table 3 Catalyst Ni content (%) AHYD1 (%) A HYD2 (%) A (non-compliant) 27 75 75 B (non-compliant) 27 76 80 C (compliant) 24 160 170 D (compliant) 27 180 195 E (non-compliant) 22 <1 <1 E (non-compliant) 22 100 100

[0153] These results clearly demonstrate a significant improvement in the performance of catalysts C and D obtained by the preparation process according to the invention, in A HYD1 and A HYD2, compared to the non-conforming catalysts A, B, and E. For catalysts A and B, nickel oxide is reduced by 90% at 170°C and exhibits particles that grew larger during the NiCu impregnation step in the absence of the second organic compound. Catalyst E shows reduced activity due to the absence of NiCu and therefore the near-zero reducibility of NiO at 170°C. Catalysts C and D retain small nickel particles due to the addition of malonic acid (the second organic compound) during the post-treatment addition of NiCu, compared to the addition of the nickel active phase precursor.

Claims

1. Process for preparing a catalyst comprising nickel and copper, in a proportion of 1% and 50% by weight of nickel element relative to the total weight of the catalyst, and in a proportion of 0.5% to 15% by weight of copper element relative to the total weight of the catalyst, and a porous alumina support, the size of the nickel particles in the catalyst, measured in oxide form, being less than 5 nm, which process comprises at least the following steps: a) the alumina support is brought into contact with at least one solution containing at least one first nickel precursor and at least one first organic compound comprising at least one carboxylic acid function to obtain a first catalyst precursor; b) the first catalyst precursor obtained at the end of step a) is dried at a temperature of less than 250°C and then the dried first catalyst precursor is calcined at a temperature of between 250°C and 550°C to obtain a calcined catalyst precursor; c) the calcined catalyst precursor obtained at the end of step b) is brought into contact with at least one solution containing at least one second nickel precursor, at least one copper precursor and at least one second organic compound comprising at least one carboxylic acid function to obtain a second catalyst precursor; d) the second catalyst precursor obtained at the end of step c) is dried at a temperature of less than 250°C.

2. Process according to Claim 1, wherein the mole ratio between said organic compound introduced in step a) and the nickel element also introduced in step a) is between 0.01 and 5.0 mol / mol.

3. Process according to either of Claims 1 and 2, wherein the mole ratio between said organic compound introduced in step c) and the nickel element also introduced in step c) is between 0.02 and 5 mol / mol.

4. Process according to any one of Claims 1 to 3, wherein the mole ratio between the nickel introduced during steps a) and c) and the copper introduced in step c) is between 0.5 and 5 mol / mol.

5. Process according to any one of Claims 1 to 4, wherein the ratio between the mole ratio between the second organic compound and the nickel introduced in step c) and the mole ratio between the first organic compound and the nickel introduced in step a) is greater than 1.5.

6. Process according to any one of Claims 1 to 5, wherein steps a) and b) are carried out at least twice before carrying out step c).

7. Process according to any one of Claims 1 to 6, wherein the first organic compound of step a) and the second organic compound of step c) are chosen from oxalic acid, malonic acid, glycolic acid, lactic acid, tartronic acid, citric acid, tartaric acid, pyruvic acid and levulinic acid.

8. Process according to any one of Claims 1 to 7, wherein the first organic compound of step a) and the second organic compound of step c) are identical.

9. Process according to any one of Claims 1 to 8, wherein the copper precursor is chosen from copper acetate, copper acetylacetonate, copper nitrate, copper sulfate, copper chloride, copper bromide, copper iodide and copper fluoride.

10. Process according to any one of Claims 1 to 9, wherein the first nickel precursor and / or the second nickel precursor are / is nickel nitrate, nickel chloride, nickel acetate or nickel hydroxycarbonate.

11. Process according to any one of Claims 1 to 10, further comprising a step e) wherein the catalyst obtained at the end of step d) is calcined at a temperature of between 250°C and 550°C.

12. Process according to any one of Claims 1 to 11, further comprising a step f) wherein the catalyst obtained at the end of step d), optionally obtained at the end of step e), is reduced by bringing said catalyst into contact with a reducing gas at a temperature of greater than or equal to 150°C and less than 250°C.

13. Catalyst obtained via the process according to any one of Claims 1 to 12, said catalyst comprising nickel and copper, in a proportion of 1% and 50% by weight of nickel element relative to the total weight of the catalyst, and in a proportion of 0.5% to 15% by weight of copper element relative to the total weight of the catalyst, and a porous alumina support, the size of the nickel particles in the catalyst, measured in oxide form, being less than 5 nm.

14. Process for the selective hydrogenation of polyunsaturated compounds containing at least 2 carbon atoms per molecule, contained in a hydrocarbon feedstock having a final boiling point below or equal to 300°C, which process being carried out at a temperature of between 0°C and 300°C, at a pressure of between 0.1 and 10 MPa, at a hydrogen / (polyunsaturated compounds to be hydrogenated) mole ratio of between 0.1 and 10 and at an hourly space velocity of between 0.1 and 200 h-1 when the process is carried out in the liquid phase, or at a hydrogen / (polyunsaturated compounds to be hydrogenated) mole ratio of between 0.5 and 1000 and at an hourly space velocity of between 100 and 40 000 h-1 when the process is carried out in the gas phase, in the presence of a catalyst according to Claim 13 or obtained according to the preparation process according to any one of Claims 1 to 12.

15. Process for the hydrogenation of at least one aromatic or polyaromatic compound contained in a hydrocarbon feedstock having a final boiling point below or equal to 650°C, said process being carried out in the gas phase or in the liquid phase, at a temperature of between 30 and 350°C, at a pressure of between 0.1 and 20 MPa, at a hydrogen / (aromatic compounds to be hydrogenated) mole ratio of between 0.1 and 10 and at an hourly space velocity of between 0.05 and 50 h-1, in the presence of a catalyst according to Claim 13 or obtained according to the preparation process according to any one of Claims 1 to 12.